Voltage adjustment

Thread Starter

Mnemoseck

Joined Apr 18, 2013
2
I am about 10 years removed from Circuit design so pardon me for being a bit rusty. I have a 6vdc to 40vdc signal that I want to clip at a 0 - 24vdc signal to trigger a relay. This is coming from the auxiliary port on a desk phone and I wanted to convert this into a "line in use" light. If I can get the voltage down I can connect to a relay and then I 'm good from there. I however am confused which direction to go and which components to pick. If I can get started on the right path I should be ok, if anyone can give a few suggestions.
 

wayneh

Joined Sep 9, 2010
17,504
Does the signal have enough current to trigger your relay directly? There are solutions that could use the signal to trigger a comparator, for instance, that would then control the relay. But that would would require a DC power supply to power the circuit.

If you have enough juice at your trigger and the relay doesn't require too much, I'm thinking you could use a current-limiting resistor and a zener to cap the input to the relay.
 

#12

Joined Nov 30, 2010
18,224
Here's an idea: Why activate a relay coil when they require so much more energy than an LED? Why not just add a resistor and a light?
 

Thread Starter

Mnemoseck

Joined Apr 18, 2013
2
You're right with the LED. The only benefit of doing a relay is that I can trigger anything, like a 120Vac Desk lamp. There is enough current draw. I can trigger the realy but the voltage doesn't drop low enough to releas it. I also have a controller at my desk that I can read the voltage into and incorporate it into a program for various other functions if it was scaled properly. I could simplify it down to an LED, and that would defiantly serve my purposes for now. Over complicating it also helps refresh my memory on alot of aspects.

Thanks.
 
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